1. Field of the Invention
The present invention relates generally to electrically conductive surfaces that are submerged and, more particularly, to submerged surfaces that conduct electricity for the purpose of generating electrochemical changes near the surface to inhibit the growth of marine organisms.
2. Description of the Related Art
Those skilled in the art of marine vessel design and other submerged surfaces are familiar with techniques that can be used to inhibit the growth of marine organisms on those surfaces. It is known that, in sea water, electrolysis can be used to create gaseous chlorine on or near the surfaces of submerged devices, such as boat hulls or grates used in conjunction with submerged intake pipes. The chlorine discourages the growth of marine organisms on those surfaces.
U.S. Pat. No. 6,173,669, which issued to Staerzl on Jan. 16, 2001, discloses an apparatus and method for inhibiting fouling of an underwater surface. The fouling prevention system comprises two conductive surfaces and a device that alternates the direction of electric current between the two surfaces. The current is caused to flow through sea water in which the two surfaces are submerged or partially submerged. A monitor measures the current flowing from one of the two conduction surfaces and compares it to the current flowing into the other conductive surface to assure that no leakage of current of substantial quantity exists.
U.S. Pat. No. 6,209,472, which issued to Staerzl on Apr. 3, 2001, discloses an apparatus and method for inhibiting fouling of an underwater surface. The system for inhibiting marine organism growth on underwater surfaces provides an electric current generator which causes an electric current to flow proximate the underwater surface. A source of power, such as a battery, provides electrical power to the electric current generator. The flow of current passes from the underwater surface through the water surrounding the surface or in contact with the surface, and a point of ground potential. The point of ground potential can be a marine propulsion system attached to a boat on which the underwater surface is contained.
U.S. Pat. No. 6,514,401, which issued to Chyou et al. on Feb. 4, 2003, describes an anti-biofouling system. The system is adapted to be used for an underwater structure immersed in seawater. The anti-biofouling system includes a conductive layer, comprising carbon or graphite fiber, carbon or graphite powder, and binder, formed on a surface of the underwater structure for serving as an anode, a cathode, and a power supply for providing a current, thereby performing an electrolytic reaction for the anti-biofouling system such that a fouling organism is prohibited from attaching on the surface of the underwater structure.
U.S. Pat. No. 6,547,952, which issued to Staerzl on Apr. 15, 2003, discloses a system for inhibiting fouling of an underwater surface. An electrically conductive surface is combined with a protective surface of glass in order to provide an anode from which electrons can be transferred to seawater for the purpose of generating gaseous chlorine on the surface to be protected. Ambient temperature cure glass (ATC glass) provides a covalent bond on an electrically conductive surface, such as nickel-bearing paint. In this way, boat hulls, submerged portions of outboard motors, and submerged portions of sterndrive systems can be protected effectively from the growth of marine organisms, such as barnacles.
U.S. Pat. No. 6,572,997, which issued to Iqbal et al. on Jun. 3, 2003, describes nanocomposites for fuel cell bipolar plates. An electrically conductive flow field plate in a proton exchange membrane fuel cell comprises a composition made of a resin and a plurality of carbon nanotubular fibers having an average diameter which is at least about 0.5 nm and up to about 300 nm. The carbon nanotubular fibers are present at not more than about 85 wt. %. The resin can be of a thermoplastic type, a fluorinated type, a thermosetting type, and a liquid crystalline type.
U.S. Pat. No. 6,844,567, which issued to Talroze et al. on Jan. 18, 2005, describes conductive polymer materials and methods of their manufacture and use. Quantum nanowires are produced in a medium comprising ions, dopants and free electrons, wherein the free electrons are celebrated by complexes of ions and dopants. Electrical conductivity of the quantum nanowires can be higher than for conventional metal conductors.
U.S. Pat. No. 6,919,063, which issued to Jang et al. on Jul. 19, 2005, describes carbon nanoparticles and methods of preparing the same. The invention relates to a novel carbon nanoparticle and a novel method of preparing the same and a transparent, conductive polymer composite containing the same. The carbon nanoparticle has the mean diameter of 1 through 50 nm and the shape of a sphere, rod, or others, which is a novel material not known in the relevant art. The carbon nanoparticle has the excellent electric conductivity and the ferromagnetic property and can be made by a novel, low-cost method entirely different from those of fullerene and carbon nanotube.
U.S. Pat. No. 6,670,607, which issued to Wood et al. on Dec. 30, 2003, describes a conductive polymer coated nanoelectrospray emitter. The emitter includes an emitter body which includes a fluid inlet, an outlet orifice, and a passage communicating between the fluid inlet and outlet orifice.
U.S. Pat. No. 6,936,653, which issued to McElrath et al. on Aug. 30, 2005, describes composite materials comprising polar polymers and single-wall carbon nanotubes. The invention relates to a composite comprising a weight fraction of single-wall carbon nanotubes and at least one polar polymer wherein the composite has an electrical and/or thermal conductivity enhanced over that of the polymer alone.
U.S. Pat. No. 6,973,890, which issued to Staerzl on Dec. 13, 2005, discloses a self-adaptive system for an apparatus which inhibits fouling of an underwater surface. The system is provided which automatically calibrates the marine fouling prevention system. It responds to movements between fresh and saltwater bodies of water, detects damage to the hull or other submerged surfaces, and responds to the use of the fouling prevention system with different sizes of marine vessels.
U.S. Pat. No. 6,986,853, which issued to Glatkowski et al. Jan. 17, 2006, describes carbon nanotube fiber reinforced composite structures for electromagnetic and lightening strike protection. A method for repairing fiber reinforced composite structures while maintaining original electromagnetic and lightening protection using carbon nanotubes, fibers, and thermoset resins is described.
U.S. Pat. No. 7,011,884, which issued to Chow et al. on Mar. 14, 2006, describes a carbon nanotube with a graphitic outer layer. A method for manufacturing carbon nanotubes with an integrally attached outer carbon layer is disclosed. The graphitic layer improves the ability to handle and manipulate the nanometer size nanotube device in various applications, such as a probe tip in scanning probe microscopes and optical microscopes, or as an electron emitting device.
U.S. Pat. No. 7,025,013, which issued to Staerzl et al. on Apr. 11, 2006, discloses a multilayered submersible structure with fouling inhibiting characteristics. The structure has an outer coating that is disposed in contact with water in which the structure is submerged, the current distribution layer or charge distribution layer, an electrical conductor connectable in electrical communication to a source of electrical power, and a support structure.
U.S. Pat. No. 7,109,136, which issued to Senecal et al. on Sep. 19, 2006, describes conductive polymer membrane articles and methods for producing the same. It comprises a non-woven membrane of polymer fibers, wherein at least some of the fibers have diameters of less than one micron.
U.S. Pat. No. 7,131,877, which issued to Staerzl on Nov. 7, 2006, discloses a method for protecting a marine propulsion system. An electrically conductive coating is provided on a housing structure of a marine propulsion system. By impressing a current on the electrically conductive coating, which can be a polymer material, the housing structure is used as an anode in a cathodic protection system. In addition, the use of the electrically conductive coating on the housing structure as an anode inhibits the growth of marine fouling on the outer surface of the housing structure by forming chlorine gas in a saltwater environment and by forming an acidic water layer near the surface in a non-saltwater environment.
U.S. Pat. No. 7,147,966, which issued to Ren et al. on Dec. 12, 2006, describes coated carbon nanotube array electrodes. The conductive carbon nanotube (CNT) electrode materials comprise aligned CNT substrates coated with an electrically conductive polymer, and the fabrication of electrodes for use in high performance electrical energy storage devices. In particular, the present invention provides CNT material whose electrical properties render them especially suitable for use in high efficiency rechargeable batteries.
U.S. Pat. No. 7,211,173, which issued to Staerzl et al. on May 1, 2007, discloses a system for inhibiting fouling of an underwater surface. The system comprises first and second conductors which are made of a polymer matrix, such as vinyl ester, and a suspended conductor, such as carbon powder or particles. This type of conductive material is formed to provide two sections of a boat hull so that a source of electrical current can be used to reversibly cause an electric current to flow to and from the conductive coatings. The conductive coatings are electrically insulated from each other in order to force the formation of an electrical circuit which includes the two conductive coatings, the source of electrical current, and the water in which the boat hull is disposed. This results in the creation of chlorine bubbles on the conductive surfaces. Chlorine bubbles on the boat hull surfaces discourage the formation of marine growth, such as barnacles.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
Various types of nanoparticles have been developed and used in recent years. It has been discovered that nanoparticles exhibit improved characteristics, such as conductivity, in comparison to larger particles of the same material. In addition, many different systems for inhibiting biofouling on submerged surfaces have been developed. Since the beginning of the 20th century, it has been known that the electrolytic creation of various gases, such as chlorine, discourages the growth of marine organisms on submerged surfaces. However, during almost a century of development, an efficient, cost effective, and robust system for discouraging marine growth without the use of poisons has proved difficult to achieve. It would therefore be significantly beneficial if a system could be provided to efficiently create electrically conductive surfaces that operate in an effective and robust manner to discourage biofouling on submerged surfaces.